Palladium Catalyzed C3-(sp)-H Alkenylation of Pyrroles via a Benzothiazole Directing Group: A Direct Access to Organic Thermally Activated Delayed Fluorescence Materials.

A Pd (II)-catalyzed direct C3-(sp)-H alkenylation of heteroarenes using benzothiazole as a directing group was successfully achieved. A wide range of 2--alkylpyrroles undergo an oxidative coupling with a variety of acrylates to furnish highly regio- and chemoselective E-alkenylation products at the C3 position. An important intermediate complex has been isolated and characterized so as to have an insight into the mechanism. This convenient protocol proved to be practical to access thermally activated delayed fluorescence materials (TADF). These molecules proved to be blue-emitting TADF materials (∼ms lifetime). A detailed and systematic investigation has been carried out to study the photophysical properties, and this has been further validated by the time-dependent density functional theory calculations.